James W. Patterson

Rheumatoid nodule and subcutaneous granuloma annulare. A comparative histologic study

We performed histologic and selected histochemical and immunohistochemical studies on rheumatoid nodules (RN) from 12 patients and lesions of subcutaneous granuloma annulare (SGA) from nine patients. The mean age for patients with RN was 56 years, while that for SGA patients was 19 years. In contrast to those with RN, none of the patients with SGA had arthritis. RN tended to show homogeneous, eosinophilic necrobiosis, giant cells within palisaded foci, and significant stromal fibrosis; while lesions of SGA showed pale, edematous necrobiosis, an absence of giant cells, and lesser degrees of fibrosis. The single most helpful histochemical method was alcian blue, which stained necrobiotic foci in all cases of SGA but in only one case of RN. Epithelioid cells in both disorders stained positively for muramidase. IgM was found in vessel walls in two cases of RN. While the mechanisms of these disorders are not entirely clear, it appears that RN can usually be reliably distinguished from SGA on histologic grounds alone.

Onychomatricoma: report of a case and its comparison with fibrokeratoma of the nailbed.

Onychomatricoma was first described in 1992 by Baran and Kint. Twenty cases have been reported to date, all of which are from Europe. This tumor has characteristic clinical, light microscopic, and ultrastructural features which have recently been refined andjustify its categorization as a novel tumor of the nail matrix. We examined a specimen sent in consultation by a large reference laboratory; despite improper orientation and absence of the involved nail plate, it had microscopic characteristics consistent with onychomatricoma. Soon thereafter, a second patient presented with a tumor arising in the nailbed that bore a superficial resemblance to onychomatricoma but showed the microscopic features of fibrokeratoma. We discuss the differentiation between these two lesions and point out that a distinction can be made even when incomplete material is submitted for review. To our knowledge, this is the first example of onychomatricoma to be reported from North America.

Lichenoid histopathologic changes in patients with clinical diagnoses of exfoliative dermatitis

Among 30 patients who received a clinical diagnosis of exfoliative dermatitis and were hiopsied between 1982 and 1990, nine showed microscopic features of lichenoid dermatitis. Clinical information was available in eight of these cases. Possible etiologic factors included lymphoma, herpes simplex infection, connective tissue disease, and (in five cases) reactions to drugs. In each instance, microscopic features included a superficial perivascular lymphocytic infiltrate involving the dermal-epidermal interface, vacuolar alteration of the basilar layer, and individually necrotic keratinocytes at all levels of the epidermis. Such microscopic changes are not usually described in connection with exfoliative dermatitis, with the possible exception of those cases related to lichen planus or lupus erythematosus. Disseminated lichenoid drug eruption is one possible interpretation of the drug-induced cases. Erythema multiforme is another condition that has similar microscopic features and has been associated with drugs (many of which also cause exfoliative dermatitis), infectious agents, neoplasms, and connective tissue diseases. Lichenoid dermatitis can become generalized and clinically mimic an exfoliative dermatitis. Many, but not all, of these eruptions may be triggered by drugs.

An extracellular body of plasma cell origin in inflammatory infiltrates within the dermis.

During examination of a biopsy specimen of skin by conventional microscopy, numerous round, basophilic, extracellular bodies suggestive of fungal organisms were seen in the dermis. Further evaluation and special staining suggested that their origin was from the plasma cells. Examination of biopsy material from 48 patients with cutaneous plasma cell infiltrates revealed similar bodies in 20 cases (42%). Sizes of bodies varied, the largest being 5.0 µm in diameter. In every case, staining reactions were identical to those of plasma cell cytoplasm. Immunoperoxidase methods showed that, like plasma cells, the bodies contained either κ or λ light chains. In one case of plasmacytoma associated with multiple myeloma, both the bodies and the surrounding neoplastic cells stained for κ chains only. Electron microscopy revealed rounded structures composed of aggregates of rough endoplasmic reticulum, which contained varying amounts of moderately electron-dense material within the cisternae. Fragmented plasma cells were also seen. The evidence suggests that plasma cell bodies are distinct from Russell bodies. They probably form as a result of trauma during processing of tissue, but could also represent a degenerative process in vivo. They should be distinguished from pathogenic micro-organisms and other extracellular bodies.

Diagnostic histochemistry in non-neoplastic skin diseases

Non-neoplastic skin lesions comprise a sizable group of disorders with variable etiologies and clinical manifestations. They can be grouped into vesiculopustular dermatitides; spongiotic and psoriasiform diseases; lichenoid dermatitides; lymphoid infiltrates of the dermis; granulomatous processes; bullous disorders; vasculopathies; panniculitides; deposition disorders; and defects in maintenance of dermal connective tissue. The use of histochemical methods continues to be an indispensable adjunct to conventional microscopy in the further characterization of such lesions. This review considers that topic.