Measurement of Depth of Premammary Fascia and Breast Parenchyma by Sonography and Histological Quantitation

Most surgical texts recommend the skin flap elevation in mastectomy at a plane between small and large fat lobules. However, raising a skin flap at this plane results in necrosis of skin in 10 to 15% cases. Objective of mastectomy is to remove the tumor along with entire breast parenchyma containing ducto-lobular units. Pre-mammary fascia is interposed between subcutaneous fat and breast parenchyma. Most of the terminal ducto-lobular units (TDLUs) reach superficially the plane of pre-mammary fascia. Raising a skin flap superficial to pre-mammary fascia would allow the surgeon to remove most of the breast parenchymal tissue without leaving any TDLUs under the flaps. The depth of pre-mammary fascia was measured by ultrasound in 50 patients at four spots, one in each quadrant of the breast before mastectomy. The distance between dermis and nearest TDLU was measured histologically at the same four spots in 50 mastectomy specimens. Maximum depth of pre-mammary fascia by sonography was observed in upper outer quadrant (UOQ) (mean = 1.8 cm) and minimum in lower inner quadrant (LIQ) (mean = 1.2 cm). Histologically maximum depth of TDLU was found in UOQ (mean = 1.9 cm) and the minimum depth in the LIQ (mean = 1.3 cm). There was a very strong correlation between sonographic and histologic measurements (Pearson’s rho = 0.93). This study demonstrated that ducto-lobular tissue is located deep to pre-mammary fascia. Skin flap elevation at the plane of pre-mammary fascia would ensure complete removal of breast tissue during mastectomy.