Three phases of lichenoid reactions are defined: 1) the primary phase, 2) the established phase; and 3) the senescent phase. Lichen striatus is characterized by a primary pattern that may be apparent in the epidermis, the hair follicles, and rarely the sweat glands and ducts. Focal areas of established lichenoid reaction, that are indistinguishable from lichen planus, are common. They usually are confined to the tips of elongated rete ridges. Established lichenoid patterns are occasionally present in hair follicles and are indistinguishable from those seen in lichen planopilaris. Eccrine hidradenitis, a feature of lichen striatus, is rarely seen in lichen planus. Lichen planus may be an adaptive epidermal response to a clone of aggressive lymphocytes and, as such, may be a manifestation of auto-immunity. In lichen striatus, senescent lichenoid patterns resemble those seen in lichen nitidus.

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Parachordoma is a soft tissue tumor that has a light microscopic appearance similar to that of chordoma, and the immunostaining properties of the two tumors are alike. The clinical findings and light microscopy of one case of parachordoma are presented together with ultrastructural observations on this tumor and parachordomas from five additional patients.

The minute chemodectomas of the lung belong to the paraganglioma group of neoplasms, which include carotid and aortic body tumors. They are frequently multiple, small in size, and are nearly always detected fortuitously on histologic examination of sections of a lung taken from an older patient. They are believed to arise from the normal chemoreceptors of the lung. There is no indication that these small neoplasms are functional. It has been proposed that pulmonary chemodectomas may be induced by pulmonary thromboemboli. This possibility gains some support from an analysis of 10 new cases and a review of 46 cases previously reported.