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Several points can be made from analysis of the published cases of cutaneous mycobacteriosis and those in our series: 1) mycobacterial cutaneous infections are probably more common than is reported-we collected 34 cases over a 10-year period; 2) most patients with cutaneous infections caused by nontuberculous mycobacteria have significant underlying disease; 3) there is a relative lack of classic histologic features in patients with cutaneous mycobacteriosis, and there appear to be diverse forms of clinical presentation; 4) a high index of suspicion is needed in evaluating patients with possible cutaneous mycobacteriosis, and appropriate cultures must be done to establish the diagnosis. In attempting to provide a practical classification of cutaneous mycobacteriosis which includes infection by nontuberculous mycobacteria, we propose the following grouping, which uses simple terms, avoids confusing nomenclature, and incorporates pathophysiologic descriptions and prognostic information: 1) Mycobacteriosis caused by inoculation from an exogenous source. 2) Cutaneous mycobacteriosis caused by spread from an endogenous source. Contiguous spread originates most often with osteomyelitis, but also occurs through autoinoculation of the perirectal, oral, or vaginal skin as organisms are passed or expectorated from pulmonary or genitourinary tuberculosis. 3) Cutaneous mycobacteriosis caused by hematogenous spread. This group includes lupus vulgaris, nodules and abscesses, and acute disease with hemorrhagic pustules. Some mycobacterioses will be difficult to classify when inoculation or hematogenous spread cannot be ruled out. However, the system of classification we have proposed should help clinicians understand and diagnose the diverse forms of cutaneous mycobacterial infections.

Fibrous papules on the nose from two patients were examined by electron microscopy. In each, the large characteristic dermal cells had ultrastructural features of fibroblasts, and there was no evidence of either melanocytic or Schwann cell differentiation. Banded structures (long-spacing collagen) were present in one case.

Two cases of verruciform xanthoma of the vulva are described. This rare lesion, previously reported to occur only in the oral cavity, is characterized by a verrucous epithelial proliferation accompanied by xanthoma cells distributed exclusively in the papillary dermis. The histologic features of the lesion are diagnostic and include (1) regular acanthosis in which the rete pegs extend to a uniform level into the dermis; (2) hyperkeratosis with parakeratosis often extending deep into the rete pegs and manifesting a massive neutrophilic infiltrate; (3) hyalinization of the collagen and infiltrates of xanthoma cells that are restricted to the papillary dermis between the rete pegs. Additionally, a lichenoid inflammatory infiltrate is seen at the periphery of the verrucous lesions, and in one case this has the pattern of classic lichen sclerosus. Verruciform xanthoma must be differentiated from verruca vulgaris, condyloma acuminatum, granular cell tumor with pseudoepitheliomatous hyperplasia, and verrucous carcinoma.

A case of streptococcal bacteremia presenting with disseminated nodular lesions is presented. Although the incidence of group A streptococcal bacteremia has declined, the disease may affect both normal and immunologically compromised children. Early recognition and prompt antibiotic therapy are required to ensure a favorable outcome.

While performing an electron microscopic examination of the skin for diagnostic purposes, we observed a cluster of cells with dense-core membrane-bound granules in the external root sheath of a hair follicle. The finding of Merkel cells in hair follicle could help to explain some histogenetic features of neuroendocrine tumors of the skin.

A cervical root tumor in a patient with neurofibromatosis showed a biphasic pattern of spindle and epitheloid cells with prominent "gland" formation, characteristic of the so-called glandular schwannoma. Electron microscopy and histochemistry of the "glands" disclosed features consistent with an ependymal differentiation. It is noted that there is a curious preferential association of ependymal lesions and neurofibromatosis, the pathogenesis of which is not understood.