A rare malignant blue nevus resected from the back of a 34‐year‐old Caucasian woman is reported. Histopathologic examination showed the presence of a CBN as well as MBN. The CBN elements of this lesion showed the characteristic prominent neural type fascicles intertwined with melanocytes. The deeper regions of this skin neoplasm showed considerable variation in histopathologic patterns. Metastascs to the axillary lymph nodes and multiple subdermal soft tissue sites, invasion of the underlying skeletal muscle, and several recurrences in the chest wall indicate that this neoplasm is malignant, though of a lower order than a malignant melanoma. The ultrastructural characteristics of neoplastic cells indicate that this neoplasm is of Schwann cell origin.

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A fluoride resistant acid phosphatase reaction (pH 5.0) has been demonstrated histochemically in the cuticular border of the mouse duodenum. This reaction was shown to be inactivated by the metal chelating agent, ethylene diamine tetraacetic acid, and reactivated by the following metallic salts : calcium chloride, cobalt(ous) nitrate, cupric sulfate, ferric chloride, ferric ammonium sulfate, ferrous sulfate, lead nitrate, lithium sulfate, magnesium sulfate, mercuric chloride, manganous chloride and zinc acetate. The two ferric salts produced the greatest amount of reactivation and cupric sulfate and manganous chloride produced the least amount of reactivation. These characteristics of inactivation by a metal chelating agent and metal reactivation plus the fluoride resistance of the acid phosphatase reaction present in the cuticular border of the mouse duodenum are features more typical of an alkaline type of phosphatase rather than the acid variety. This suggests that alkaline type phosphatase may be demonstrable histochemically in the cuticular border of the mouse duodenum in the acid pH range.

Tumors were induced in the small intestine, forestomach, and lungs of strain A/jax mice by feeding olive oil emulsions containing 20-methylcholanthrene. Histochemical methods were used to determine the occurrence and distribution of acid and alkaline phosphatase in the tissues of the mice. The tumors generally showed a complete absence of alkaline phosphatase and widely varying quantities of acid phosphatase in the cytoplasm of the individual cells. Tumors of the small intestine and forestomach showed a high concentration of alkaline phosphatase in the submucosal zone immediately beneath the neoplasm. No enzyme changes from normal were detected in lesions considered histologically to be premalignant. Some groups of mice were fed iron choline citrate or ethylenediamine tetraacetic acid, tetrasodium salt in addition to 20-methylcholanthrene. These substances produced no effect on the rate of growth or numbers of tumors induced, nor on the acid and alkaline phosphatase reactions.