Ossifying Plexiform Tumor: Report of Two New Cases

Abstract

Ossifying plexiform tumor is a cutaneous lesion that microscopically resembles cellular neurothekeoma but has abundant central ossification as the prominent feature and has only been previously described in a single case report. We detail 2 additional examples, both arising on the finger of adult women (36 and 76 years old). Clinically, the lesions were described as a raised flesh-colored "extraosseous" mass, averaging 1.1 cm in greatest dimension. Histological examination showed an unencapsulated well-delineated dermal tumor with thin fibrous bands separating lobules and fascicles of epithelioid to spindled cells that were embedded in a somewhat loose myxoid matrix. Present within the center of the lobules were large irregular foci of mature bone, some lined by osteoblasts. After excision, these lesions have not recurred or persisted in a limited follow-up duration (9 and 2 months). In concordance with the only other case report of a 30-year-old woman with a left thumb mass, ossifying plexiform tumor has occurred exclusively on the digits of adult women. Although it is possible that ossifying plexiform tumor could represent an ossifying variant of cellular neurothekeoma, we believe it is a lesion sui generis, and hope its recognition will allow for an accurate diagnosis and distinction from other cutaneous ossifying lesions.

Ossifying plexiform tumor

“…Previous reports show the tumor cells to be non‐reactive for numerous antibodies including S100, MSA, AE1/AE3, EMA and neurofilament . NKI/C3 and NSE, which are almost always positive in cellular neurothekeomas, were also negative . S100A6 has been reported to be positive in cellular neurothekeoma, but the same report also showed 100% of cellular neurothekeomas to be positive for NK1‐C3, suggesting that ossifying plexiform tumor is not a ossifying variant of cellular neurothekeoma.…”

“…Roony et al reported the case in a 30‐year‐old female with a left thumb lesion that measured 1.6 cm. Walsh and Sangueza reported a case in a 76‐year‐old female with lesion on the left long finger measuring 1.3 cm, and a 36‐year‐old female with a 0.9‐cm right index finger lesion. Our case is a 2‐cm right thumb lesion in a 64‐year‐old female.…”

“…Ossifying plexiform tumor is a rare entity of yet unknown etiology. It has been reported twice in the past literature, once as an isolated case report and then as a pair of two cases . The initial report by Rooney et al described a dermal lesion with a plexiform architecture, showing lobules of spindled tumor cells in a myxoid background, and characteristic bone formation in the center of the lobules .…”

“…It has been reported twice in the past literature, once as an isolated case report and then as a pair of two cases. 1,2 The initial report by Rooney et al described a dermal lesion with a plexiform architecture, showing lobules of spindled tumor cells in a myxoid background, and characteristic bone formation in the center of the lobules. 1 The second report showed similar histopathologic findings and described additional staining results that refuted a previously proposed relationship between ossifying plexiform tumor and neurothekeoma.…”

Cutaneous Deposits

“…In some tumors, such as ossifying plexiform tumor and ossifying fibromyxoid tumor, ossification is one of the characteristic histopathologic features. 88,89 One of the authors (L.C.) has observed ossification with formation of bone marrow in the context of chondrodermatitis nodularis helicis.…”