OBJECTIVES:Diagnosis of adenoid cystic carcinoma (ACC) in salivary gland cytology specimens may be challenging due to overlapping features with cellular pleomorphic adenoma and monomorphic adenomas. Due to this difficulty, some are classified as salivary gland neoplasm of uncertain malignant potential. Criteria exist for the diagnosis of ACC but have not been statistically validated. This study analyzes the utility of published criteria for this purpose. METHODS:A series of 46 salivary gland tumors (26 ACC and 20 other basaloid neoplasms) were investigated by logistic regression analysis for the utility of 11 criteria used in the diagnosis of ACC. RESULTS:The reproducibility of these criteria was fair to moderate (Cohen's kappa 0.2473-0.5482). Logistic regression showed that the presence of hyaline stroma and absence of plasmacytoid cells, myxoid stroma, or nuclear palisading supports the diagnosis of ACC. CONCLUSIONS:The presence of hyaline stroma supports the diagnosis of ACC. While cell rings and "finger in glove" structures were frequently seen in ACCs, they were not found to be useful according to the logistic regression analysis for the diagnosis of ACCs.

Fine needle aspiration procedure is routinely used for cytological diagnosis of nodal or extra nodal lesions. Follicular dendritic cell sarcoma (FDCS) is a rare mesenchymal neoplasm arising from follicular dendritic cells of lymphoid follicles at nodal and extranodal sites. Multimodal therapies have emerged for FDCS, necessitating its accurate pathologic diagnosis with additional ancillary testing for directing clinical management. By immunohistochemical analysis, FDCS is positive for the complement receptors CD21, CD23, and CD35. In addition, D2-40 is reported to be highly sensitive for FDCS with a strong membranous pattern of expression. In this study, we present the cytological diagnosis of a case of FDCS in retroperitoneal lymph nodes with an emphasis on a unique staining pattern of D2-40 which showed a strong nuclear pattern in tumor cells comparable to the membranous pattern of D2-40 on the control tissue and other surgical cases of FDCS in our comparative study.

INTRODUCTION:In 2024, the World Health Organization (WHO) is scheduled to publish the WHO Reporting System for Soft Tissue Cytopathology (WHORSSTC). This system establishes categories with well-defined definitions, criteria, and estimated risks of malignancy (ROMs) for soft tissue tumors. The estimates of ROM are based on a relatively small number of published studies. Interobserver reproducibility is not addressed in the reporting system even though reproducibility of a reporting system is highly important. METHODS:A manual search of one authors personal consultation files and teaching set (L.J.L.) was conducted for all cytologic specimens of soft tissue tumors accessioned between January 1, 1985 and December 31, 2022. Only cases with documented surgical pathology follow-up were included in the study. Slides from each case were evaluated independently by three cytopathologists with each case assigned to one of the WHORSSTC categories. A ROM for each of the WHORSSTC categories was calculated. Interobserver agreement was evaluated by the kappa and weighted kappa statistics. RESULTS:Risk for malignancy by category were: Category 1: 0%, Category 2: 28%, Category 3: 57%, Category 4: 47%, Category 5: 63%, and Category 6: 88%. Kappa statistics for agreement between raters varied from 0.2183 to 0.3465 and weighted kappa varied from 0.3778 to 0.5217. CONCLUSIONS:The WHORSSTC showed a progression of malignancy risk from the category "benign" (28%) to the category "malignant" (88%). Interobserver agreement was only fair.

Supplementary Data - PDF file 1112K, Supplementary Figures 1-6 and Supplementary Tables 1&2

Anaplastic thyroid carcinoma is an infrequent, but aggressive fatal subtype of thyroid cancer. The osteoclastic variant of anaplastic carcinoma is a rare subtype of anaplastic carcinoma with rare cases reported in the literature. Molecular targeted therapies have emerged for the anaplastic carcinoma, necessitating accurate pathologic diagnosis with additional ancillary testing for directing clinical management. We present here the cytological diagnosis of an anaplastic thyroid carcinoma-osteoclastic variant on fine-needle aspiration (FNA), with emphasis on the novelty of utilizing the least invasive procedure (aspiration cytology) for rendering pathological diagnosis as well as identifying potential prognostic markers for targeted immunotherapy.

Many crystals and crystal-like structures may be encountered in cytopathology practice and can represent both beautiful novelties and diagnostic aids. The authors present an organ-specific review of the published literature on crystals combined with personal experiences. The purpose is not only to serve as a reference guide by highlighting the clinical and morphologic features of crystals, crystalloids, and crystal-like structures but also to review their significance and to offer reporting strategies in cases that bear management implications.

Spindle cell/sclerosing rhabdomyosarcoma (RMS), characterized by MYOD1 (L122R) mutation in a subset of cases is a newly described subtype of RMS. Presently, there is no documentation of cytomorphological features, especially of sclerosing RMS. Case 1: A 24-year-old male presented with pain and swelling in his wrist for a one-year duration. MRI revealed a well-defined soft tissue lesion measuring 5.3 cm, encasing the lower end of the ulna. Fine-needle aspiration cytology (FNAC) smears revealed clusters of tumor cells with round to oval to spindle-shaped nuclei, scant to moderate amount of cytoplasm with the wisps of the metachromatic stroma. Histopathological examination revealed a malignant tumor comprising cells with polygonal to spindle-shaped nuclei, arranged in a sclerotic stroma. Immunohistochemically, the tumor cells were positive for desmin, myogenin, and MYOD1. A diagnosis of sclerosing RMS was offered. Furthermore, the tumor revealed MYOD1 (L122R) mutation. Case 2: A 43-year-old male presented with a 4-month history of "nasal stuffiness" and pressure. Imaging revealed a poorly defined infiltrative lesion in his nasal cavity. FNAC smears revealed loose and tightly cohesive clusters of malignant cells with oval to spindle-shaped nuclei, a moderate amount of ill-defined bluish to finely vacuolated cytoplasm, and focal streak artifact with interspersed stromal fragments. Histopathological examination revealed a malignant tumor composed of oval to spindle-shaped nuclei, embedded in a variably hyalinized stroma. Immunohistochemically, the tumor cells were positive for desmin, and myogenin. Diagnosis of spindle cell/sclerosing RMS was offered. The present study constitutes one of the first documentation of cytomorphological features of two rare cases of spindle cell/sclerosing RMS. The differential diagnoses and treatment-related implications are presented.

•Some Pap tests show features intermediate between LSIL and HSIL with consequent poor reproducibility.•Review by 11 observers of 21 such slides confirmed poor reproducibility and identified only number of HSIL and ASC-H cells as statistically correlated with correct classification from among 11 variables.

BACKGROUND:Immunotherapy is increasingly used for treatment of metastatic melanoma and carcinomas. PD-1 (programmed death 1) and its associated ligand (PD-L1) inhibits the activation of T-lymphocytes. This inhibition can be impacted by a number of drugs. Response to these drugs is predicted by assessment of PD-L1 expression. PD-L1 expression varies between 19% and 92% in melanomas and carcinomas. PD-L1 expression is less well documented for sarcomas.DESIGN:Fifty-six sarcomas of various histopathologic types were immunohistochemically stained (IHC) for PD-L1 using the antibody clone SP263 (Ventana, Tuscan, AZ). Membrane staining of tumor cells was quantitated as a percentage of total tumor cells. Sarcomas were judged as non-expressors (less than 1%) low-expressors (1 to 50%) and high expressors (greater than 50%). The percentage of each type of sarcoma judged as an expressor was determined.RESULTS:Table 1 documents the percentage of each type of sarcoma expressing PD-L1. 14% of sarcomas expressed PD-L1. Percentage of sarcomas expressing PD-L1 varied significantly between types but the majority of sarcomas were non-expressors.CONCLUSION:PD-L1 IHC expression is valuable in predicting response to immune-modulating drugs. Such therapies may be useful for treatment of metastatic sarcomas. Expression of PD-L1 in carcinomas and melanomas is variable ranging from 19% to 92%. In our study, a minority (14%) of sarcomas expressed PD-L1. Other studies have shown similar results with between 1.4 and 59% (average 24%) of sarcomas expressing PD-L1. Expression appears to be sarcoma type specific. These finding suggest that PD-L1 based therapy may be less useful in sarcomas than in other malignancies.

IntroductionThe accurate diagnosis of musculoskeletal neoplasms is difficult but a pattern-based approach combined with ancillary testing has been shown to improve diagnostic accuracy. The pattern-based approach is particularly appropriate for myxoid lesions.Materials and methodsThe authors reviewed their personal experience of over 3 decades of diagnosing myxoid neoplasms of musculoskeletal lesions.ResultsThe authors found that myxoid lesions can be accurately classified based on cell type, nuclear atypia, presence of blood vessel fragments, as well as the results of immunohistochemical and molecular testing.ConclusionsMusculoskeletal lesions with a prominence of myxoid or chondroid material in the background can be accurately diagnosed using pattern analysis and ancillary testing.

Giant cell tumor of bone (GCT) is a benign locally aggressive neoplasm composed of mononuclear cells admixed with innumerable osteoclast-type giant cells. H3F3A gene mutations producing mutant histone protein product H3.3 have been identified in 96% of GCT; mutant H3.3 is reliably demonstrated by immunohistochemistry. GCT may contain woven bone and rarely, neoplastic cartilage nodules which causes diagnostic challenges with aggressive neoplasms such as osteosarcoma. We describe the features of GCT with cartilage matrix and report the next-generation sequencing findings in a subset of tumors. Seventeen cases of GCT with cartilage matrix form the cohort: 7 males and 10 females, 13 to 55 (mean: 25) years old. Tumors involved the fibula (6), femur (6), and patella, tibia, humerus, S1, and scapula (1 case each). Tumors were radiolucent, circumscribed, lytic, and expansile. All contained classic GCT, foci of cartilage matrix, and trabeculae of woven bone. Immunohistochemistry showed diffuse staining for H3.3 in 9/9 cases and 1 case was positive for S100 and SOX9 in the cartilage areas. Next-generation sequencing showed a mutation in the H3F3A gene in 6/6 cases. On follow-up, 2 patients who underwent resection showed no disease after 12, and 7 months, respectively. Three patients had recurrences 10, 12, and 27 months after curettage; there were no metastases. GCT with cartilage matrix is uncommon. The cartilage matrix is associated with woven bone suggesting the neoplastic cells may differentiate into chondrocyte-like and osteoblast-like cells. Recognition of this neoplasm is important to prevent misdiagnosis and overtreatment of affected patients.

Background Approximately twenty percent of lymph node (LN) negative non-small cell lung cancer (NSCLC) patients who undergo curative intent surgery have pan-cytokeratin immunohistochemistry (IHC)-detectable occult micro-metastases (MMs) in resected LNs. The presence of the MMs in NSCLC is associated worsened outcomes. As a substantial proportion of NSCLC LN staging is conducted using endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA), we sought to determine the frequency of detection of occult MMs in EBUS-TBNA specimens and to evaluate the impact of MMs on progression-free and overall survival. Methods We performed retrospective IHC staining for pan-cytokeratin of EBUS-TBNA specimens previously deemed negative by a cytopathologist based on conventional hematoxylin and eosin staining. The results were correlated with clinical variables, including survival outcomes. Results Of 887 patients screened, 44 patients were identified meeting inclusion criteria with sufficient additional tissue for testing. With respect to the time of the EBUS-TBNA procedure, 52% of patients were clinical stage I, 34% clinical stage II, and clinical 14% stage IIIa NSCLC. Three patients (6.8%) were found to have cytokeratin positive MMs. All 3 MMs detected were at N2 LN stations. The presence of MMs was associated with significantly decreased progression-free (median 210 vs. 1,293 days, P=0.0093) and overall survival (median 239 vs. 1,120 days, P=0.0357). Conclusions Occult LN MMs can be detected in EBUS-TBNA specimens obtained during staging examinations and are associated with poor clinical outcomes. If prospectively confirmed, these results have significant implications for EBUS-TBNA specimen analyses and possibly for the NSCLC staging paradigm.

Post-transplant lymphoproliferative disorders (PTLD) are a known risk for both solid organ transplant and stem cell transplant recipients. Overall transplant recipients have a six fold increase in risk for developing any kind of non-Hodgkin lymphoma and PTLDs occur in up to 10% of SOT recipients. Several new entities have been accepted or renamed in the 2018 update of the WHO classification of tumors of hematopoietic and lymphoid neoplasms, including florid follicular hyperplasia and extranodal marginal zone lymphomas of mucosa-associated lymphoid tissue (MALT-lymphoma) (excluding common locations such as stomach and salivary gland). Other more rare types of PTLD have been reclassified including EBV-positive mucocutaneous ulcer, which is now a recognized diagnosis in its own right and should not be considered polymorphous PTLD. In this paper newly recognized PTLD entities and more unusual PTLDs will be examined.

Introduction: The Papanicolaou Society of Cytopathology (PSC) has developed a set of guidelines for reporting respiratory cytology. While the malignancy risk for each category is known, the interobserver reproducibility of these diagnostic categories has not been well described. Methods: Fifty-five cytologic specimens obtained by fine needle aspiration from the pulmonary nodules were independently reviewed by four board-certified cytopathologists and assigned to the diagnostic categories described by the PSC guidelines for respiratory specimens. Statistical analysis for diagnostic accuracy was performed for absolute agreement and chance-corrected agreement (kappa). Differences in frequency of distribution of diagnoses between raters were assessed using the Kruskal–Wallis test. Results: No significant differences in distribution of scores by raters were observed. On average, the absolute agreement was 49.5% and the chance-corrected agreement (kappa) was 20%. 34.5% of interrater comparisons were in full agreement, and total lack of agreement between the four categories was found in 3% of cases. Combining the “suspicious for malignancy” category with the “malignant” category did not significantly alter interrater agreement statistics. Conclusions: The PSC categories showed only fair reproducibility among four cytopathologists. Agreement between raters was at best fair and did not improve significantly when the categories “suspicious for malignancy” and “malignant” were combined. The most common source of disagreement appeared to be between the categories “suspicious” and “malignant.”

CONTEXT.—:Obtaining diagnostic concordance for squamous intraepithelial lesions in cytology can be challenging.OBJECTIVE.—:To determine diagnostic concordance for biopsy-proven low-grade squamous intraepithelial lesion (LSIL) and high-grade squamous intraepithelial lesion (HSIL) Papanicolaou test slides in the College of American Pathologists PAP Education program.DESIGN.—:We analyzed 121 059 responses from 4251 LSIL and HSIL slides for the interval 2004 to 2013 using a nonlinear mixed-model fit for reference diagnosis, preparation type, and participant type. We evaluated interactions between the reference diagnosis and the other 2 factors in addition to a repeated-measures component to adjust for slide-specific performance.RESULTS.—:There was a statistically significant difference between misclassification of LSIL (2.4%; 1384 of 57 664) and HSIL (4.4%; 2762 of 63 395). There was no performance difference between pathologists and cytotechnologists for LSIL, but cytotechnologists had a significantly higher HSIL misclassification rate than pathologists (5.5%; 1437 of 27 534 versus 4.0%; 1032 of 25 630; P = .01), and both were more likely to misrepresent HSIL as LSIL ( P < .001) than the reverse. ThinPrep LSIL slides were more likely to be misclassified as HSIL (2.4%; 920 of 38 582) than SurePath LSIL slides (1.5%; 198 of 13 196), but conventional slides were the most likely to be misclassified in both categories (4.5%; 266 of 5886 for LSIL, and 6.5%; 573 of 8825 for HSIL).CONCLUSIONS.—:More participants undercalled HSIL as LSIL (false-negative) than overcalled LSIL as HSIL (false-positive) in the PAP Education program, with conventional slides more likely to be misclassified than ThinPrep or SurePath slides. Pathologists and cytotechnologists classify LSIL equally well, but cytotechnologists are significantly more likely to undercall HSIL as LSIL than are pathologists.

To determine if concomitant high-risk human papillomavirus (HPV-HR) reflex testing may bias the cytologic interpretation of Papanicolaou (Pap) tests. Percentage of atypical squamous cells of undetermined significance (ASCUS) and HPV-HR positivity was compared between Pap tests with HPV-HR cotesting and HPV-HR reflex testing for ASCUS, with subset analysis of cytopathologists' experience. ASCUS in the reflex group (41.5%) was significantly higher than the cotesting group (33.0%) (P = .02). There was no difference in HPV-HR positivity or ASCUS/squamous intraepithelial lesion (SIL) ratios between the two groups. The cytopathologists' experience inversely correlated with the proportion of ASCUS but did not explain the higher reflex group ASCUS. HPV-HR reflex testing may introduce bias in cytologic diagnosis, making it more likely that an ASCUS diagnosis is rendered. HPV-HR and ASCUS/SIL ratios were similar between the groups, so cytopathologist performance was not significantly affected. There was no effect of cytopathologists' experience.

The CIC-DUX4 sarcoma is a small round blue cell sarcoma which presents like extraskeletal Ewing sarcoma, but is negative for the EWSR1 gene translocation. The recognition of CIC-DUX4 sarcomas as an aggressive sarcoma may be challenging in fine needle aspirates or small needle core biopsies. We present a case of a 13-year-old female with a fine needle aspiration (FNA) and core needle biopsy (CNB) of a thigh mass showing CIC-DUX4 sarcoma. Cytologic findings include tumor cells with high nuclear to cytoplasmic (N:C) ratio, eccentric nuclei and small nucleoli. The tumor cells were arranged in sheets and singly dispersed with background necrosis. Mitotic figures and apoptosis were present. These findings are similar to cases previously reported. Other reported findings of spindled nuclei, clear cell change and lobular growth pattern were not seen in our case. Immunohistochemical stains showed tumor cells positive for CD99, WT1, vimentin and negative for pancytokeratin, desmin and myogenin, which is the pattern similar to cases previously reported. However, our case was also positive for BCL-2. Fluorescence in situ hybridization (FISH) was negative for EWSR1 and SS18 (SYT) rearrangements and positive for CIC gene rearrangement. On balance, if the following features are seen: (1) a small round blue cell tumor with histomorphology more atypical than that of Ewing sarcoma, (2) cytoplasmic CD99 staining, nuclear WT1 positivity, negative keratin, desmin and myogenin; and (3) EWSR1 rearrangement negative by FISH, then molecular testing for CIC-DUX4 sarcoma should be considered.