Allen

 
"The decision as to whether or not a given lesion is to be diagnosed an active junctional nevus or a melanocarcinoma must, when juvenile melanomas are excluded, depend on this single fact: the presence or absence of dermal invasion. It is to be stressed, however, that awesomely little evidence of dermal downgrowth of malignant cells is required for the diagnosis of melanocarcinoma, as opposed to junctional nevus. Often, isolated or clusters of invading cells are recognized among the subepidermal lymphocytes by their circular shape and abundant spongy cytoplasm, finely sprinkled with granules of melanin. They are to be distinguished particularly from histiocytes or reticulum cells. The subepidermal zone of lymphocytes is usually present in both the activated junctional nevus and the superficial melanocarcinoma." (Fig. 4) Allen AC. The Skin. A clinicopathologic treatise. St. Louis: The C. V. Mosby Company, 1954:868.

View Figure  		Fig. 4   Our diagnosis and comment: Melanoma in situ. The term "active junctional nevus" is wrong in all respects; activity cannot be observed through a microscope, the abnormal melanocytes are not situated only at the dermo-epidermal junction, and the lesion is not a nevus. Allen acknowledged that the neoplasm is a melanoma by stating, " . . . this lesion is equivalent to a melanocarcinoma in situ." In actuality, however, melanoma is a sarcoma, not a carcinoma.
 

Brief Critique

 
The idea of identifying "invasion" on morphologic grounds is wholly without justification; a compound nevus, such as Spitz's, is no less invasive, as judged morphologically than a melanoma of equal thickness. In fact, a Spitz's nevus often is more invasive biologically because of its capability for more rapid growth than melanoma, evidenced by readily discernible mitotic figures in many Spitz's nevi. In actuality, histopathologists make a determination of invasion based on reasoning in post hoc ergo propter hoc fashion: if a neoplasm is deemed to be benign, for example, a Spitz's nevus, it is said not to be invasive, but if a neoplasm of the same thickness is thought to be malignant, for example, melanoma, it is then claimed to be invasive.
 
In short, Allen provided no criteria for distinguishing melanoma from Spitz's nevus.