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Calcified chondroid mesenchymal neoplasm is a recently recognized bone and soft tissue entity primarily found in the extremities and the temporomandibular joint. This neoplasm is typically driven by the fusion of the FN1 gene with a kinase. In this case report, we provide a detailed account of a rare superficial calcified chondroid mesenchymal neoplasm located on the left big toe, characterized by an FN1::FGFR2 fusion. The tumor exhibited a peripheral collarette and consisted of large intradermal histiocytoid to epithelioid cells with no mitotic activity. These cells displayed fine chromatin and abundant pale eosinophilic cytoplasm, forming a swirling syncytium. They were interspersed with localized areas of glassy chondromyxoid matrix containing randomly mineralized calcific material and isolated osteoclast‐like giant cells. RNA sequencing confirmed the presence of an FN1 (exon 29)::FGFR2 (exon 7) gene fusion. Our report emphasizes the importance for dermatopathologists to consider this entity when evaluating superficial lesions displaying mesenchymal, chondroid, and calcified attributes. [ABSTRACT FROM AUTHOR]

Background: The immunohistochemical (IHC) marker PReferentially expressed Antigen in MElanoma (PRAME) has shown promise in the diagnosis of melanocytic lesions. A few studies have investigated PRAME IHC expression in acral melanomas, but PRAME expression in subungual melanomas is largely unknown. We evaluated the utility of PRAME IHC expression in distinguishing subungual melanomas (SUM) and non‐subungual acral melanomas (AM) from acral nevi (AN). Methods: Twenty‐two SUM, 20 AM, and 14 AN were identified. IHC studies were performed using an anti‐PRAME antibody. The percentage of lesional cells with PRAME expression was recorded and categorized as follows: 0%, 0; 1%–25%, 1+; 26%–50%, 2+; 51%–75%, 3+; and >75%, 4+. Patient demographics and other relevant clinicopathologic parameters were recorded. Results: Diffuse (4+) PRAME IHC expression was identified in 55% (12/22) SUM and 70% (14/20) AM, respectively. Any PRAME expression (1+ to 4+) was identified in 73% (16/22) SUMs and 95% (19/20) AM, respectively. One of 14 (7%) AN exhibited PRAME expression; interestingly, the pattern of expression was diffuse. Conclusions: In our study, PRAME IHC expression was useful in identifying AM, including SUM. However, there are exceptions of PRAME‐negative melanomas and PRAME‐positive nevi. [ABSTRACT FROM AUTHOR]

Acral melanocytic neoplasms often pose diagnostic difficulty. Preferentially expressed antigen in melanoma (PRAME) expression and loss of p16 expression have diagnostic utility in melanocytic tumors. We examined PRAME and p16 expression in 30 acral melanocytic neoplasms (n = 11 nevi; n = 2 dysplastic nevi; n = 7 Spitz nevi; n = 10 acral melanomas). PRAME was scored as % positive nuclei: negative = 0%; 1% to 25% = 1+; 25% to 50% = 2+; 50% to 75% = 3+, or positive: 75% to 100% = 4+. p16 expression was defined as retained (homogeneous or checkerboard) or lost (complete or partial/regionally). PRAME expression was negative in all benign, dysplastic, and Spitz nevi. Conversely, all acral melanomas were diffusely (4+) positive for PRAME expression. p16 expression was retained in all benign acral nevi (8/11 homogeneous, 3/11 checkerboard), completely lost in one dysplastic nevus, and retained in all acral Spitz nevi (3/7 homogeneous, 4/7 checkerboard). p16 was retained in five of 10 acral melanomas (3/10 homogeneous; 2/10 checkerboard), and negative in five of 10 acral melanomas (absent in 3/10, partially lost in 2/10). Our data suggest that 4+ PRAME expression is highly sensitive and specific in the setting of acral melanomas and is a more predictive diagnostic tool compared with p16 immunohistochemistry. [ABSTRACT FROM AUTHOR]

Primary cutaneous acral CD8+ T‐cell lymphoma (PCACTL) is currently a provisional entity defined as a rare cutaneous proliferation of atypical CD8+ lymphocytes that preferentially involves acral sites and has a good prognosis. We present a case of primary cutaneous CD8+ T‐cell lymphoma involving the eyelid of an adolescent male. The case shares features with PCACTL, including indolent clinical behavior and expression of CD68 in a Golgi‐associated dot‐like pattern; however, other features differ significantly from PCACTL as currently defined by the World Health Organization (WHO). These features include ulceration, expression of CD56, granzyme B, and perforin, and a high proliferative index. Given these discrepancies, our case is currently best classified as a CD8+ primary cutaneous peripheral T‐cell lymphoma, not otherwise specified. We review the differential diagnosis for this case and suggest expanding the definition of PCACTL. [ABSTRACT FROM AUTHOR]

We report the largest series to date (N = 6) of EWSR1‐SMAD3 rearranged fibroblastic tumor. Initially described in 2018, the tumor features a marked female predominance (F:M, 5:1, mean age 44‐years, median age 45.5 years; range 27‐57), with most cases (5/6, 83%) arising in acral locations (4 on foot/toe, 1 on hand). One case presented on the lower extremity. The lesions presented as nodules and were composed of short, variably cellular, intersecting fascicles of uniform spindled cells in a collagenous to myxoid stroma. In four cases, the tumor abutted the epidermis without a grenz zone. In one case, there was an abrupt transition to a central, acellular hyalinized area. Two other cases had admixed smaller collagenous areas, reminiscent of collagen rosettes. One had a concentric arrangement of tumor cells around blood vessels. Mitotic activity was low (<1/10 HPFs). All were positive for ERG by immunohistochemistry and negative for CD34 (6/6). An EWSR1‐SMAD3 fusion was identified in three cases tested by next‐generation sequencing (3/3). Rearrangement of EWSR1 by fluorescence in situ hybridization was showed in 1/1 case. Our series reaffirms prior findings and expands the known histopathologic spectrum of this emerging entity. [ABSTRACT FROM AUTHOR]

Acral localized acquired cutis laxa (ALACL) is a rare variant of acquired cutis laxa, and the clinical appearance is characterized by loose, redundant and wrinkled skin of the distal extremities. By definition, histopathology of affected tissue reveals sparse or fragmented elastic fibers. However, this can be difficult to assess on routine staining, and sometimes requires electron microscopy. The condition has been associated with plasma cell dyscrasias or recurrent inflammatory states. We present a case of a 65‐year‐old man who presented with enlarged and doughy finger pads. Skin biopsy showed diffuse dermal amyloid deposition displacing dermal stroma and reduction of elastic fibers, although these changes were subtle on routine hematoxylin and eosin staining. Mass spectrometry of laser capture microdissected tissue showed AL kappa‐type amyloid and further workup revealed a diagnosis of primary systemic AL‐kappa amyloidosis requiring bone marrow transplantation. This case represents an unusual presentation of acquired cutis laxa and highlights the need for a high index of suspicion when reviewing histopathology of this entity. In addition, the case highlights the importance of investigation into possible systemic associations, such as plasma cell dyscrasias. [ABSTRACT FROM AUTHOR]

Background Primary cutaneous indolent CD8-positive lymphoid proliferation is an emerging entity characterized by slowly enlarging papules and nodules that are pathologically comprised of clonal nonepidermotropic medium-sized atypical CD8(+) T-cells. Although the majority of lesions are solitary and located on the ears, bilateral symmetrical presentations have been described and lesions may arise at other peripheral or 'acral' sites. Patients follow a benign clinical course and systemic involvement has not yet been observed. Despite this, some medical practitioners classify such lesions as peripheral T-cell lymphoma, NOS, a category implying aggressive disease. Objectives We present three cases seen in our institutions and provide an update on a previously reported unique patient who continues to develop recurrent and multifocal skin lesions. Results Systemic disease progression has not been observed, even in the presence of recurrent and multifocal cutaneous disease. Conclusions Indolent CD8-positive lymphoid proliferation of acral sites is a distinctive and readily identifiable entity and should be included in the next consensus revision of cutaneous lymphoma classification. Although cases described thus far have followed an indolent clinical course, dermatologists should remain guarded about the prognosis and full staging and longitudinal observation are recommended until this condition is better understood. [ABSTRACT FROM AUTHOR]