Speckled lentiginous nevus (SLN), also referred to as nevus spilus, is a common benign melanocytic neoplasm typically occurring as a small, café-au-lait-colored "speckled" patch studded with numerous darkly pigmented macules or papules. Herein, we present a unique case of SLN arising on the sole of the right foot in a young woman, which was reported to be gradually enlarging since a pregnancy two years prior. The lesion was removed by shave biopsy, and histopathology confirmed the diagnosis and ruled out atypical features. While SLN is quite common, the occurrence on acral skin is extremely rare. SLN is considered a mosaic RASopathy due to its embryological development through a postzygotic activating HRAS genetic variant. Although small lesions usually remain isolated, underlying SLN syndrome should be considered in extensive cases with associated neurologic or musculoskeletal abnormalities. Secondary melanocytic neoplasms commonly arise within SLN, but overall, small lesions carry a low risk of malignant transformation, and prophylactic surgical treatment is not necessary. We briefly discuss SLN occurring in special sites and report this novel case with a review of the literature on SLN.

Lichen planus pigmentosus is an uncommon subtype of lichen planus and lichen planus pigmentosus inversus is a rare variant of lichen planus pigmentosus. Lichen planus pigmentosus inversus typically presents as hyperpigmented patches or plaques, particularly in the intertriginous areas such as the axillae, the groin and inguinal folds, and in the submammary region. In some patients with lichen planus pigmentosus inversus, the condition can present as a pigmented lichenoid axillary inverse dermatosis (PLAID) when the lesions are in the axillae. A 49 -year -old Hispanic man who had hyperlipidemia and diabetes mellitus developed lichen planus pigmentosus inversus and presented with a PLAID. Skin biopsies established the diagnosis of lichen planus pigmentosus inversus. The clinical differential diagnosis of lichen planus pigmentosus inversus includes inherited disorders, primary cutaneous dermatoses, acquired dyschromias, and reactions to topical or systemic medications. Friction in intertriginous areas has been related to the development of lichen planus pigmentosus inversus. Factors that can precipitate lichen planus pigmentosus inversus include not only topical exposure to almond oil, amala oil, cold and cosmetic creams, henna, and paraphenyldiamine but also either topical contact or consumption of mustard oil and nickel. Lichen planus pigmentosus inversus can be associated with autoimmune conditions (hypothyroidism), endocrinopathies (diabetes mellitus), and hyperlipidemia. The dyschromia found in patients with lichen planus pigmentosus inversus is frequently refractory to treatment. Initial management includes removal of potential disease triggers such as eliminating tight clothing to stop friction with the adjacent skin. Topical corticosteroids do not result in improvement; however, topical calcineurin inhibitors such as tacrolimus have been reported to be efficacious. In conclusion, inverse lichen planus and lichen planus pigmentosus inversus can present with a PLAID; whereas topical corticosteroids may be helpful to resolve inverse lichen planus lesions, topical tacrolimus may be useful to improve the dyschromia in lichen planus pigmentosus inversus.

A halo phenomenon describes a skin neoplasm that is surrounded by a hypopigmented or white halo. Halo lesions have been observed in association with an epithelial neoplasm (seborrheic keratosis), a fibrous lesion (surgical scar), a keratinocyte malignancy (basal cell carcinoma), melanocytic neoplasms, and vascular lesions. Benign lesions (café au lait macules and nevi) and malignant tumors (primary and metastatic melanoma) are melanocytic neoplasms that have developed perilesional halos. Halo nevi are a commonly occurring manifestation of a halo phenomenon; however, perilesional hypopigmented halos have also been observed around nevi in patients following treatment with antineoplastic drugs, acquisition of COVID-19 (infection and vaccine), the occurrence of a visceral tumor (including not only melanoma, but also papillary thyroid carcinoma and neuroendocrine cancer of the lung), surgery (such as the excision of a primary melanoma), and Turner syndrome. A halo phenomenon has also been observed in patients with congenital (capillary malformation-arteriovenous malformation and congenital hemangioma) or acquired (angioma, eruptive pseudoangiomatosis, infantile hemangioma, and lobular capillary hemangioma) vascular lesions. In summary, a halo phenomenon can occur in association with primary lesions of various embryologic derivations. Most commonly, they have been observed in around nevi and vascular tumors. Halo lobular capillary hemangioma can be added to the list of acquired vascular lesions with the potential to develop a halo phenomenon. The preservation of melanocytes with loss of melanin pigment expression in the reported patient suggests the possibility that a post-inflammatory etiology may be responsible for the genesis of her halo lobular capillary hemangioma.

Calcinosis cutis describes the deposition of calcium in the dermis. A case of a 69-year-old woman with idiopathic calcinosis cutis that presented as a mobile subcutaneous nodule is described. The patient had an asymptomatic, firm, mobile subcutaneous nodule on her right lower leg of at least six months duration. The nodule could be easily moved from one location to another. An incisional biopsy was performed. Microscopic examination of the tissue specimen showed islands of basophilic calcium material in dense sclerotic dermal connective tissue establishing the diagnosis of calcinosis cutis. Mobile solitary calcification is an unusual presentation of idiopathic calcinosis cutis. In addition to idiopathic calcinosis cutis, benign mobile subcutaneous tumors have also been derived from adnexal structures of hair follicles and adipose tissue. Hence, not only idiopathic calcinosis cutis, but also subepidermal calcinosis in the ocular adnexa, proliferating trichilemmal cyst with focal calcification, and mobile encapsulated adipose tissue can present as a mobile subcutaneous nodule. The features of idiopathic calcinosis presenting as a mobile subcutaneous nodule as well as the characteristics of other benign mobile subcutaneous tumors are reviewed.

Perivascular epithelioid cell tumor (PEComa) expresses melanocytic and smooth muscle markers. A man with a primary malignant cutaneous (distal left forearm) PEComa is reported. Immunohistochemistry demonstrated MiTF, HMB-45, caldesmon, desmin, and smooth muscle actin, as well as BCL1, CD10, and CD68. Next generation sequencing showed four pathogenic genomic aberrations involving BIRC3, FANCC, TP53, and TSC1 genes. His work-up was negative for metastatic disease; a wide local excision was performed. Including the reported patient, cutaneous PEComa has been described in 65 individuals: primary benign (N=58), primary malignant (N=5), and metastatic malignant (N=2). Cutaneous PEComa typically presented as a painless, slowly growing nodule of <2 centimeters on the lower extremity of a woman in her fifth decade. The neoplasms consisted of epithelioid cells, spindle cells, or both. The most reliable markers were MiTF (100%), HMB45 (94%), and NKIC3 (94%) for melanocytes and smooth muscle actin (43%) and desmin (40%) for smooth muscle. There has been no reported recurrence of a primary cutaneous benign or malignant PEComa after complete excision. Genomic alterations in malignant PEComas frequently involve TSC1 and TSC2 genes (mTOR activators), as well as TFE3 fusions. In November 2021, the FDA approved nab-sirolimus (mTOR inhibitor) for PEComas.

References 1 Batra RS, Kelley LC. Predictors of extensive subclinical spread in nonmelanoma skin cancer treated with mohs micrographic surgery. Arch Dermatol. 2002;138(8):1043–51. 2 Ralli M, Pandey P, Agarwal S, J C. Adenoid basal cell carcinoma presenting as ulceroproliferative nodule nose-a rare histopathological variant. Biomed J Sci Tech Res. 2018;2 (1):2200–3. 3 Tambe SA, Ghate SS, Jerajani HR. Adenoid type of basal cell carcinoma: Rare histopathological variant at an unusual location. Indian J Dermatol. 2013;58(2):159. 4 National comprehensive cancer network (NCCN). NCCN clinical practice guidelines in oncology. [cited 2022 May 5]. Available from: https://www.nccn.org/guidelines/category_1 5 Seretis K, Thomaidis V, Karpouzis A, Tamiolakis D, Tsamis I. Epidemiology of surgical treatment of nonmelanoma skin cancer of the head and neck in Greece. Dermatol Surg. 2010;36(1):15–22.

Fungal infections may occur within tattoos. These include not only dermatophyte infections (tattoo-associated tinea) but also systemic mycoses (tattoo-associated systemic fungal infections). The PubMed search engine, accessing the MEDLINE database, was used to search for all papers with the terms: (1) tinea and tattoo, and (2) systemic fungal infection and tattoo. Tattoo-associated tinea corporis has been observed in 12 individuals with 13 tattoos; this includes the 18-year-old man who developed a dermatophyte infection, restricted to the black ink, less than one-month after tattoo inoculation on his left arm described in this report. Tattoo-associated tinea typically occurred on an extremity in the black ink. The diagnosis was established either by skin biopsy, fungal culture, and/or potassium hydroxide preparation. The cultured dermatophytes included Trichophyton rubrum, Epidermophyton floccosum, Microsporum canis, Microsporum gypseum, and Trichophyton tonsurans. Several sources for the tinea were documented: autoinfection (two patients), anthrophilic (tinea capitis from the patient's son), and zoophilic (either the patient's cat or dog). Three patients presented with tinea incognito resulting from prior corticosteroid treatment. Tinea appeared either early (within one month or less after inoculation during tattoo healing) in six patients or later (more than two months post-inoculation in a healed tattoo) in six patients. Injury to the skin from the tattoo needle, or use of non-sterile instruments, or contaminated ink, and/or contact with a human or animal dermatophyte source are possible causes of early tinea infection. Tattoo ink-related phenomenon (presence of nanoparticles, polycyclic aromatic hydrocarbons, and cytokine-enhancement) and/or the creation of an immunocompromised cutaneous district are potential causes of late tinea infection. Treatment with topical and/or oral antifungal agents provided complete resolution of the dermatophyte for all the patients with tattoo-associated tinea. Tattoo-associated systemic fungal infection has been reported in six patients: five men and one patient whose age, sex, immune status, and some tattoo features (duration, color, and treatment) were not reported. The onset of infection after tattoo inoculation was either within less than one month (two men), three months (two men), or 69 months (one man). The tattoo was dark (either black or blue) and often presented as papules (three men) or nodules (two men) that were either individual or multiple and intact or ulcerated. The lesion was asymptomatic (one man), non-tender (one man), or painful (one man). The systemic fungal organisms included Acremonium species, Aspergillus fumigatus, Purpureocillium lilacinum, Saksenaea vasiformis, and Sporothrix schenckii. Contaminated tattoo ink was a confirmed cause of the systemic fungal infection in one patient; other postulated sources included non-professional tattoo inoculation, infected tattooing tool and/or ink in an immunosuppression host, and contaminated ritual tattooing instruments and dye. Complete resolution of the tattoo-associated systemic fungal infection occurred following systemic antifungal drug therapy. In conclusion, several researchers favor that tattoo inoculation can be implicated as a causative factor in the development of tattoo-associated tinea; however, in some of the men, tattoo-associated systemic fungal infection may have merely been coincidental.

A verruca is a human papillomavirus-associated infection of the mucosal or cutaneous epithelium. Cutaneous squamous cell carcinoma is an invasive skin cancer that commonly occurs on sun-exposed locations. Human papillomavirus infection has also been demonstrated to be a cocarcinogen, along with ultraviolet radiation, in the pathogenesis of cutaneous squamous cell carcinoma. A 63-year-old man presented with a verrucous nodule of nine months duration on his dorsal left hand. The clinical differential diagnosis included a wart and a small punch biopsy of the lesion showed a verruca. The lesion continued to enlarge and the possibility of a squamous cell carcinoma was considered. A second larger shave biopsy of the residual lesion was performed and the microscopic evaluation revealed not only a benign verruca at the lateral portion of the nodule but also an invasive squamous cell carcinoma in the center of the lesion. We hypothesize that the patient's human papillomavirus-associated wart may have contributed to the development of his cutaneous squamous cell carcinoma. Therefore, in an individual with a clinically suspected or biopsy-confirmed wart that persists despite lesion-directed treatment, additional evaluation of the lesion should be considered to assess whether an alternative or concurrent tumor, such as a cutaneous squamous cell carcinoma, is present.

Frontal fibrosing alopecia is lymphocytic scarring alopecia most commonly affecting postmenopausal women. Alopecia syphilitica, an uncommon manifestation of secondary syphilis, is characterized as a nonscarring and non-inflammatory hair loss that primarily affects the scalp. Frontal fibrosing alopecia has a classic pattern of hair loss involving regression of frontotemporal hair; it also may affect the eyebrows or other sites of the body. The typical patterns of frontal fibrosing alopecia are characterized as diffuse and linear. In addition, patients with frontal fibrosing alopecia can have atypical signs and patterns of hair loss. The atypical signs and patterns of frontal fibrosing alopecia are the androgenetic-like pattern, clown alopecia pattern, cockade-like pattern, doll hairline sign, lonely hair sign, ophiasis-like pattern, pseudo-fringe sign, and upsilon pattern. We observed a woman with a traditional pattern of frontal fibrosing alopecia whose hair loss involved the frontotemporal scalp areas; however, she also had hair loss in the occipital scalp that appeared similar to the moth-eaten alopecia of alopecia syphilitica. Her rapid plasma reagin was negative and the biopsies from her frontal scalp and occipital scalp both showed scarring alopecia consistent with frontal fibrosing alopecia. Her alopecia persisted with conservative treatment, and she returned to wearing a wig. Alopecia syphilitica-like pattern of hair loss can be added to the other atypical patterns of alopecia that may potentially be observed in a patient with frontal fibrosing alopecia.

A traumatic neuroma occurs at the injury site of a peripheral nerve; however, albeit rarely, this variant of a neuroma can involve a nerve that has not experienced penetrating trauma. A lower extremity amputation stump is the most common location of a traumatic neuroma. Traumatic neuromas may be symptomatic; tumor-associated pain can be severe and significantly affect the patient’s quality of life. Several hypotheses have been postulated for the pathogenesis of neuroma-related pain, including alpha-smooth muscle actin, neural fiber structural changes, nerve growth factor, and/or sensitization of the affected nerve. In addition to prevention, non-surgical treatment (such as chemical interventions, cryotherapy, neuromodulation, pharmacologic agents, and physiotherapy) and surgical interventions (such as direct nerve repair at the time of injury or ligation of the nerve proximal to the neuroma and various potential methods to minimize subsequent irritation of the distal free end of the proximal nerve) have been used to manage neuroma-associated pain. A traumatic neuroma of the nose is rare. Indeed, it has only been described in three individuals: two women (including the Caucasian woman in this report and a Turkish woman) and one man. The benign tumor was extremely painful in both women; however, the man’s lesion was non-tender. Prior trauma to the nasal site included either a laceration or elective surgery; however, the reported woman did not experience any penetrating trauma to her nose. The diagnosis was established following an excisional (for the man), incisional (for the Turkish woman), or punch (for the Caucasian woman) biopsy. Follow-up was provided for two of the patients. The man’s neuroma had been completely excised, and he never developed tumor-associated tenderness. However, the pain persisted after the biopsy healed for the reported woman whose neuroma was not entirely removed. The explosive and markedly severe character of the reported patient’s lesion-related tenderness prompted us to propose an acronym for this uncommon yet exquisitely painful variant of a neuroma: tender nasal traumatic (TNT) neuroma.

A collision tumor is a neoplastic lesion comprised of two or more tumors consisting of distinct cell populations in the concurrent location. Multiple skin neoplasms at one site (MUSK IN A NEST) is a term recently coined to describe two or more cutaneous benign or malignant tumors occurring at the same anatomic site. In retrospective studies, seborrheic keratosis and cutaneous amyloidosis have both individually been documented as a component of a MUSK IN A NEST. This report describes a 42-year-old woman who presented with a pruritic skin condition on her arms and legs of 13 years' duration. Skin biopsy results showed epidermal hyperplasia with hyperkeratosis, hyperpigmentation of the basal layer with mild acanthosis, and evidence of amyloid deposition in the papillary dermis. Based on the clinical presentation and pathology findings, a concurrent diagnosis of macular seborrheic keratosis and lichen amyloidosis was established. A MUSK IN A NEST consisting of a macular seborrheic keratosis and lichen amyloidosis is likely a more common occurrence than implied by the paucity of published cases of this phenomenon.

Background Appropriate use criteria (AUC) provide patient-centered physician guidance in test selection. An initial set of AUC was reported by the American Society of Dermatopathology (ASDP) in 2018. AUC reflect evidence collected at single timepoints and may be affected by evolving evidence and experience. The objective of this study was to update and expand AUC for selected tests. Methods RAND/UCLA (RAND Corporation [Santa Monica, CA]/University of California Los Angeles) methodology used includes the following: (a) literature review; (b) review of previously rated tests and previously employed clinical scenarios; (c) selection of previously rated tests for new ratings; (d) development of new clinical scenarios; (e) selection of additional tests; (f) three rating rounds with feedback and group discussion after rounds 1 and 2. Results For 220 clinical scenarios comprising lymphoproliferative (light chain clonality), melanocytic (comparative genomic hybridization, fluorescence in situ hybridization, reverse transcription polymerase chain reaction, telomerase reverse transcriptase promoter), vascular disorders (MYC), and inflammatory dermatoses (periodic acid-Schiff, Gomori methenamine silver), consensus by panel raters was reached in 172 of 220 (78%) scenarios, with 103 of 148 (70%) rated "usually appropriate" or "rarely appropriate" and 45 of 148 (30%), "appropriateness uncertain." Limitations: The study design only measures appropriateness. Cost, availability, test comparison, and additional clinical considerations are not measured. The possibility that the findings of this study may be influenced by the inherent biases of the dermatopathologists involved in the study cannot be excluded. Conclusions AUC are reported for selected diagnostic tests in clinical scenarios that occur in dermatopathology practice. Adhering to AUC may reduce inappropriate test utilization and improve healthcare delivery.

Verrucous xanthoma is a benign histiocytic lesion of macrophage derivation. We describe a woman with a non-mucosal verruciform xanthoma located on her right thumb and review the features of patients with verruciform acral-associated xanthoma. A 69-year-old woman presented with a lesion on her right thumb of eight years duration that had been previously treated with liquid nitrogen cryotherapy without resolution. An initial biopsy was consistent with the surface of a callous. A second biopsy demonstrated a verruciform xanthoma. The patient elected to apply lactic acid 12% twice daily and pare the lesion with a pumice stone once weekly; this resulted in flattening of the xanthoma-associated hyperkeratosis. Acral verruciform xanthoma has, albeit rarely, been described on the hands and feet of individuals. Including the patient in this report, six individuals have been reported with verrucous xanthoma on the hands and 12 individuals have been reported with a verrucous xanthoma on the feet. Verruciform xanthoma most commonly occurs on the oral mucosa. Genital lesions are also a frequent site. Acral-distributed verruciform xanthoma is rare; we propose that a verruciform xanthoma that occurs on acral sites be referred to as a verruciform acral-associated (Vacas) xanthoma.

Dermatofibromas are benign skin tumors with several variants, including the rare, uncommonly described atrophic dermatofibroma. To the best of our knowledge, there are currently 105 reported cases of atrophic dermatofibromas in the literature. This variant typically presents as a flat or depressed macule whose color can range from brown to white to red; in contrast to classic dermatofibromas that typically occur on the legs, atrophic dermatofibromas have a tendency to occur on the upper back and arms. An atrophic dermatofibroma can be clinically diagnosed; however, given the broad spectrum of clinical features of this lesion, a biopsy may be required. Characteristic pathologic features include epidermal acanthosis, basilar hyperpigmentation, fibroblast hyperplasia, and decreased or absent elastic fibers within the lesion. The pathogenesis of this lesion is not yet fully understood; however, it has been postulated that the loss of elastic fibers plays a key role in its development and characteristic atrophic appearance. We present the cases of two men with biopsy-confirmed atrophic dermatofibromas: a 47-year-old man with a pigmented macule on the right upper back and a 68-year-old man with an erythematous patch on the left posterolateral shoulder. The clinical and pathologic features of atrophic dermatofibromas are also summarized.

Basal cell carcinoma is the most common cutaneous neoplasm. Calcinosis cutis is the deposition of calcium within the dermis. An 80-year-old man presented with a pearly nodule on his left nasal ala; a shave biopsy confirmed the diagnosis of a nodular basal cell carcinoma with calcinosis cutis, which was removed with Mohs micrographic surgery. The incidence of basal cell carcinoma with calcinosis cutis as well as the classification, identification, and potential origin of calcium deposits in basal cell carcinoma are discussed. Basal cell carcinoma can be associated with calcinosis cutis; indeed, calcifying basal cell carcinoma has a calculated incidence of 14%. There are five categories of calcification in basal cell carcinoma. In addition, calcification observed in cancer-free initial sections of a suspected basal cell carcinoma may be a diagnostic clue that a neoplasm is present in deeper sections of the tissue specimen. Although nodular basal cell carcinoma has the greatest incidence (37%) of calcium deposition, infiltrative (29%) and micronodular (27%) basal cell carcinomas are also frequently associated with calcification; therefore, the presence of calcifying basal cell carcinoma may indicate a more aggressive tumor subtype. Basal cell carcinoma may also be suspected in the differential diagnosis of a superficial breast neoplasm in which calcification is observed in the dermis; in this situation, mammography has been an effective diagnostic approach for identifying the basal cell carcinoma with calcification. The pathogenesis of calcification in basal cell carcinoma remains to be definitively established; however, calcium-binding proteins found in poorly differentiated keratinocytes may contribute to the etiology of basal cell carcinoma with calcification. The treatment of basal cell carcinomas with calcinosis cutis is similar to that of non-calcifying basal cell carcinomas; it is based upon the histologic subtype, the size, and the location of the tumor.

A dystrophic nail is an alteration of the physical appearance and structural properties of the nail from its shape, color, and texture, which can result from multiple etiologies. Calcinosis cutis is a condition that refers to the calcium deposition in the skin and underlying tissue. A 55-year-old man who presented with a split right thumbnail associated with subungual calcinosis cutis affecting the same digit for a duration of nine years is described. He did not recall trauma to the affected area. Microscopic evaluation of the tissue specimen obtained following a biopsy of the affected digit's nail matrix showed foci of calcium in the dermis. The correlation of his clinical presentation and biopsy findings established a diagnosis of subungual calcinosis cutis. Subungual calcification has been observed in several clinical settings. In addition to subungual calcinosis cutis, it has been noted as a normal finding in elderly individuals. In addition, it has been observed in patients with scleroderma or following trauma to the site. Less commonly, subungual calcification can be associated with idiopathic conditions: calcifying aponeurotic fibroma, digital calcinosis circumscripta, subepidermal calcified nodule, and calcified subungual epidermoid inclusion.

A cutaneous horn, sometimes referred to as cornu cutaneum, is a projection arising on the skin due to an overgrowth of the epidermal stratum corneum. This lesion is a clinical presentation of an underlying skin tumor. A woman with a verruca vulgaris-associated cutaneous horn is described. Cutaneous horns are often solitary and appear most commonly on the face, ears, and the dorsum of the hands of older patients. The most frequent tumors associated with cutaneous horns include actinic keratoses and seborrheic keratoses; however, cutaneous horns have also been observed overlying other benign and malignant tumors. In conclusion, a cutaneous horn is a common clinical feature; however, the diagnosis of the underlying skin lesion requires a biopsy that permits adequate microscopic evaluation of the associated tumor.

Acquired digital fibrokeratoma is a benign fibrous tumor usually located on the toes and fingers. A 63-year-old man with an acquired giant plantar fibrokeratoma is described. He presented with an asymptomatic exophytic nodule of ten years duration; there is no history of trauma to the site. It measured 15x10x5mm and was located on the plantar foot proximal to the third toe. Excisional biopsy established the diagnosis of fibrokeratoma. Giant acquired fibrokeratoma,has been described in 16 patients including ours: three women and 13 men. They are located on either the upper extremity (one man) or the lower extremity (15 individuals). Acquired plantar fibrokeratoma is rare. Including our patient, it has been reported in 11 patients: one woman and ten men. The woman was 13 years of age and the men ranged from 15 to 77-years-old. Plantar acquired fibrokeratomas are located on either the plantar aspect of the toes, the sole of the foot, or the heel. An excisional biopsy provided adequate treatment without subsequent recurrence of both giant and plantar fibrokeratomas.