Cutaneous lymphocytic thrombophilic (macular) arteritis: a distinct entity or an indolent (reparative) stage of cutaneous polyarteritis nodosa? Report of 2 cases of cutaneous arteritis and review of the literature.

Recently, 2 putatively novel clinicopathological entities, macular arteritis (MA) and lymphocytic thrombophilic arteritis (LTA), have been described. Both exhibit an indolent chronic course and erythematous and hyperpigmented macules (MA > LTA) and papules/plaques (LTA > MA), often in a reticulated pattern on the lower limbs. Histopathologically, they show varying degrees of lymphocyte infiltration and disruption of the arterial wall, concentric luminal fibrin deposition, and in some cases, fibrointimal scarring (endarteritis obliterans). This spectrum of histology overlaps with the subacute, reparative, and healed stages reported for cutaneous polyarteritis nodosa (CPAN). Herein, we report 2 cases of cutaneous lymphocytic arteritis, 1 with persistent indolent disease and the second with acute self-limited disease. Comparing these 2 patients' findings with that reported for MA, LTA, and CPAN highlights a clinicopathologic spectrum, which exhibits increasing disease severity moving from MA to LTA to CPAN to systemic polyarteritis nodosa. Given the clinicopathologic similarities, we conclude that our cases and cases previously reported as MA or LTA likely represent an indolent form of CPAN.

Cutaneous myositis ossificans: an appropriate descriptor for fibro-osseous lesion of the external auditory canal.

Myositis ossificans is a benign pseudosarcomatous bone-forming lesion, histologically characterized by 2 components: a spindle (myo)fibroblastic cell population and a bony component that is arranged in a "zonal" pattern. It mainly affects the deep soft tissues of limbs, but its occurrence in other unusual locations, such as abdomen, inside nerves, and the subcutaneous fat, has been reported. The existence of myositis ossificans restricted to the skin has rarely been published under the term "fibro-osseous lesion of the external auditory canal." Here, we describe an additional case in the external auditory canal, emphasizing its differential diagnosis and alerting dermatopathologists and pathologists to the possibility of encountering such lesion in this anatomic location. For purposes of unifying terms, we propose that cases similar to ours be called "cutaneous myositis ossificans" instead of fibro-osseous lesion of the external auditory canal.

Cutaneous lipomatous sclerosing perineurioma.

Sclerosing perineurioma is a variant of extraneural soft tissue perineurioma that occurs in the distal extremities of young adults. They are composed of small, plump, spindle-shaped, or epithelioid perineurial cells that coexpress epithelial membrane antigen (EMA), glut-1, claudin 1, collagen type IV, laminin, and are negative for S-100 protein. Once locally excised, sclerosing perineurioma does not recur or metastasize. Adipocytic component has been observed occasionally in peripheral nerve sheath tumors. In particular, only one report has previously detailed histopathological features of a superficial soft tissue perineurioma harboring lipomatous areas. Herein, we report a unique case of sclerosing perineurioma showing adipocytic component. Knowledge of this phenomenon is important to reach a correct diagnosis and to avoid unnecessary aggressive local excision.