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June 26, 2019

The Second Dimension—Integrating Calculated Tumor Area Into Cancer Diagnosis

Author Affiliations
  • 1Department of Pathology and Dermatology, University of California, San Francisco
JAMA Dermatol. 2019;155(8):883-884. doi:10.1001/jamadermatol.2019.0609

As a general principle, a key indicator of the prognosis of a given primary malignant tumor is its size.1,2 Simply put, at the time of cancer diagnosis, it is better to have a small tumor than a large one. The tenet that size matters applies not only to malignant tumors developing in parenchymal organs but also cutaneous cancers. The metastatic potential of squamous cell carcinoma, the second most common cutaneous malignant condition, is highly or directly correlated with tumor size.3 At sizes smaller than a certain threshold, typically in the range of 2 mm, the risk of secondary spread is negligible. By contrast, metastases are not rare when squamous cell carcinoma exceeds 6 mm in diameter. When small (≤0.5 cm), Merkel cell carcinoma infrequently spreads to regional lymph nodes, while carcinomas of intermediate or large size exhibit higher rates of regional nodal involvement and/or multiple involved lymph nodes.4 The degree of lymph node involvement presages survival; survival is negatively correlated with the degree of lymph node involvement. Although melanoma prognostication has been based on either the Clark level or the Breslow thickness since the inception of staging, multiple investigators have also demonstrated that primary tumor volume dictates prognosis in the context of cutaneous melanoma.5-7