Agrawal, Shruti

This article describes clinical, serologic, and histopathologic features of the first North American cohort of patients with positive anti-p200 serology identified at Mayo Clinic, Rochester, Minnesota, USA and Beutner Laboratories, Buffalo, New York, USA. Forty-seven patients were identified with positive p200 laminin beta 4 autoantibodies, detected with either immunoglobulin (Ig)G or IgG4 modified indirect immunofluorescence on HEK293 cells transfected with recombinant laminin beta.

ABSTRACTVarious cutaneous adnexal neoplasms have been associated with gene fusions as the main driver of their histogenesis, most of which showed poroid or hidradenomatous differentiation or represented other tumors of sweat glands. Recently, we encountered two cases of primitive basaloid neoplasms of predominantly folliculogenic/pilosebaceous origin, both surprisingly harboring recurrent EWSR1 rearrangements. Both tumors presented in young patients of either sex (1 F; 17 years; 1 M; 37 years) and involved the dermis and subcutaneous tissue of the abdominal wall (case 1) and the buttock (case 2). Histologically, the tumors were composed of primitive, basaloid cells with areas of keratinization (case 1) or foci of sebaceous differentiation (case 2) and stained strongly with keratins, p40 (case 1) or p63 (case 2), while lacking significant CD99 expression in both cases. Case 1 harbored an EWSR1::FLI1 fusion while case 2 harbored an EWSR1::PBX3 fusion. Clinical follow‐up was available for case 2 and showed no evidence of disease at 15 months of follow‐up. Methylation profiling showed case 1 to cluster with cutaneous squamous cell carcinoma, while case 2 was independent but positioned close to salivary gland epithelial‐myoepithelial carcinoma. These findings expand on the histopathologic and molecular genetic features of basaloid tumors with apparent adnexal differentiation and raise awareness to carefully interpret and correlate molecular findings with morphology and immunophenotype to avoid misinterpretation as a mesenchymal neoplasm.

ABSTRACTBackgroundThere is a known association between common variable immunodeficiency (CVID) and granulomas in multiple organ systems, including the skin, lung, liver, and spleen. Rubella virus has also been detected within cutaneous granulomas in both immunocompetent and immunocompromised hosts. We present a retrospective case series of patients with CVID and granulomatous skin disease and describe the spectrum of clinical and histopathologic features, including the status of rubella virus in the cutaneous granulomas.MethodsWe retrospectively reviewed the clinical and histopathological characteristics of patients diagnosed with CVID at our institution, with cutaneous findings and skin biopsies available for review between 1990 and 2023, demonstrating granulomatous inflammation.ResultsEight patients met the inclusion criteria. The most common histopathologic pattern was palisaded granulomatous inflammation, seen in five of eight cases. Three cases showed strictly sarcoidal granulomas. Background inflammation was peri‐granulomatous (8/8) and the predominant background inflammatory cell type was lymphocytic (6/8). Rubella virus testing was performed for seven of eight cases and found to be positive in one case.ConclusionCutaneous granulomatous disease in CVID can present with a spectrum of clinical morphologies, granulomatous patterns, and variable rubella virus persistence. Dermatopathologists should be aware of the spectrum of findings when considering cutaneous CVID–related granulomatous disease in the differential diagnosis.

Background: Maculopapular cutaneous mastocytosis (MPCM) is a rare disorder characterized by a pathologic accumulation of mast cells in the skin, which may or may not be accompanied by systemic mastocytosis. Diagnosis of MPCM on skin biopsy can be challenging because the findings may be subtle. Although mast cell density in MPCM has been reported, data informing a proposed cutoff for diagnosis and diagnostic criteria are limited. Methods: We identified adult patients diagnosed with MPCM and urticarial tissue reaction/chronic urticaria on skin biopsy and compared the mast cell and eosinophil counts per 1 mm2 in 10 cases each of MPCM, chronic urticaria, and normal skin from routine biopsies. All slides were stained with CD117, and CD117-positive mast cells were counted per 1 mm2 using digital microscopy. Eosinophils were counted on hematoxylin and eosin-stained slides per 1 mm2 using digital microscopy. Results: The median number of mast cells per 1 mm2 was significantly higher in MPCM than in cases of urticaria and normal skin/control tissue (177.3 vs. 26.8 vs. 47.8 mast cell per mm2, respectively; P ≤ 0.001). The calculated “cut point” for mastocytosis versus chronic urticaria and normal skin was 66 mast cells per 1 mm2, whereas the value for controls versus urticaria was 37 mast cells per 1 mm2. Eosinophils had similar density in MPCM and urticaria, and their presence was significant in the differentiation of MPCM and urticaria from normal tissue. Conclusions: This study adds to the literature by providing objective mast cell density data to distinguish challenging cases of cutaneous mastocytosis from urticarial reactions and normal skin. Future studies could explore the development of computer-aided estimations of cellular density with more extensive comparison with other inflammatory conditions to translate our findings more readily into clinical practice.

Background: Following transition to digital pathology for primary diagnosis at our institution, dermatology residents have reduced exposure to light microscopy. This study compares resident competency with light microscopy versus digital pathology following practice changes. Methods: Twenty-one dermatology residents were administered a dermatopathology examination composed of 32 diagnoses evaluated using digital slides and 32 with light microscopy. Case difficulty was graded and balanced between modalities. Diagnostic accuracy was measured using the number of correct diagnoses for each modality. Participants were surveyed regarding their experience and preferences. Results: Diagnostic accuracy was higher with digital pathology than light microscopy (22/32 vs. 18/32, P < 0.001). Diagnostic accuracy with digital pathology increased with years of training, but accuracy with light microscopy did not. Residents with previous light microscopy experience achieved an average score of 19/32 on glass, as compared with 10/32 for those without experience (P = 0.039). Digital pathology was preferred over light microscopy (18/21, 85.7%). Conclusions: Trainees had better diagnostic proficiency with digital pathology and preferred this modality. Most practices at this time continue to use light microscopy. Therefore, we need to maintain proficiency in microscopy during training while concurrently preparing trainees for a digital future.

Abstract: Paratesticular mesothelioma (malignant mesothelioma arising from the tunica vaginalis of the testis) represents a small proportion of mesothelial neoplasms, and cutaneous involvement by paratesticular mesothelioma is very rare. Cutaneous involvement can manifest as scrotal subcutaneous nodules from regional spread, distant metastasis, or direct extension through surgical scars. Mesothelioma has 3 histopathologic classifications that include epithelioid, biphasic, and sarcomatoid, which is rarely seen in paratesticular mesothelioma. Given the rarity of this condition, cutaneous mesothelioma may be misdiagnosed as histologic mimics, such as metastatic adenocarcinoma or adnexal neoplasms; thus, appropriate immunohistochemical workup and clinical correlation are required to make an accurate diagnosis. In this case, a 75-year-old man with a history of paratesticular mesothelioma, status postorchiectomy, presented with right-sided scrotal swelling, erythema, and subcutaneous nodules. These nodules were identified as local recurrence with cutaneous involvement by paratesticular mesothelioma on histopathologic examination. This case highlights the clinical and histopathologic features of this diagnosis and underscores the importance of dermatopathologists being aware of this condition to ensure accurate diagnosis.

AimsThe majority of dermatofibrosarcoma protuberans (DFSP) harbour PDGFB or PDGFD rearrangements. We encountered ALK expression/rearrangement in a PDGFB/D‐negative CD34‐positive spindle cell neoplasm with features similar to DFSP, prompting evaluation of ALK‐rearrangements in DFSP and plaque‐like CD34‐positive dermal fibroma (P‐LDF).Methods and ResultsWe searched the archives of academic institutions for cases previously coded as DFSP and P‐LDF. NGS‐naïve or PDGFB‐negative DFSP were screened for ALK (clone D5F3) expression by immunohistochemistry. NGS or ALK FISH was performed on ALK‐positive cases. Methylome profiling studies were performed and compared with conventional DFSP. One case of “DFSP” and two “P‐LDF” with ALK expression were identified from the archives, while four cases were detected prospectively. These seven cases (6F:1M; 8 months to 76 years) arose in the dermis of the arm (two), scalp, eyelid, thigh, abdomen, and shoulder and ranged from 0.4 to 4.2 cm. Tumours were composed of spindled cells and displayed a storiform growth pattern. Cytologic atypia was absent, and mitotic figures were scarce (0–2/10 HPFs, high power fields). The lesional cells were diffusely positive for CD34 and ALK and negative for S100 protein. By NGS (n = 5), ALK fusion partners included DCTN1 (2), PLEKHH2, and CLIP2 in DFSP‐like cases and FLNA in P‐LDF‐like lesions. ALK FISH was positive in one (of two) cases previously labelled P‐LDF. Methylome profiling of two (of three) ALK‐rearranged DFSP‐like tumours showed clustering with conventional DFSP in the UMAP dimension reduction plot. To date, no tumour has recurred (n = 2; 26, 27 months).ConclusionWe describe a cohort of novel ALK‐rearranged tumours with morphologic features similar to DFSP.