Patient selection: pure seminoma
Criteria for intertubular growth:
(1) presence of tumor cells growing in an interstitial pattern (between the seminiferous tubules)
(2) at least 3 high powered microscopic fields (HPF) from the main circumscribed tumor (with a high powered microscopic field measuring 1 mm in diameter (0.1 cm), so there is a distance of >= 3 mm)
(3) noncontiguous with a main circumscribed tumor
where:
• The assumption is made that any growth less than 3 HPF from the main tumor mass "most likely" represents contiguous growth.
• Intertubular growth may occasionally occur in the absence of a circumscribed tumor mass.
• A focus of intertubular growth is usually not grossly evident. Detection requires generous sampling in apparently normal tissue and a careful microscopic examination.
Interpretation:
• Intertubular growth is relatively common in pure seminomas (about a third of cases).
• The presence of intertubular growth correlates with rete testis invasion and may be associated with lymphovascular spread.
Limitations:
• The authors state that the presence of intertubular growth increases the calculated size of the tumor, the rationale being that the functional diameter of the tumor should be the measurement from the far side of gross tumor to the focus of intertubular growth. I have never been convinced that this makes any sense, since it distorts the measurable volume of tumor. It should be a risk factor by itself, not used to inflate another.
