Products of Conception
Products of conception is the term used for intra-uterine tissue that is either passed spontaneously or removed surgically in early gestation. These specimens are usually sent for diagnostic or ther-apeutic purposes. The major goal is to verify that a gestation was present. This requires the identifi-cation of either fetal parts, chorionic villi, or tro-phoblastic cells. The presence of decidua alone is not sufficent for diagnosis. Molar pregnancies and placental neoplasia may also be identified, although these are much less common. Always be familiar with the patient’s clinical history, as this will help guide your examination.
Specimens from first trimester gestations are usually composed of irregularly shaped small tissue fragments and blood clots suspended with-in a fluid-filled container. Strain the entire con-tents of the container, and give an estimate of the amount of the specimen by volume (in cubic centimeters) or as an aggregate measurement. Spread the specimen across your work bench, and separate the blood clots from the tissue. Care-fully inspect the tissue for fetal parts and vil-lous tissue. Villous tissue is soft and spongy, whereas decidua is more likely to be firmer and membranous. Another method of examination is to suspend the tissue fragments in saline. The delicate villous fronds will then become readily apparent. Also, look for evidence of swollen or hydropic villi, which appear as small, grape-like vesicles.
If fetal parts are identified, measure them sepa-rately, and submit several pieces along with rep-resentative villous tissue in one or two tissue cassettes. If no fetal parts are identified and you are confident of your identification of villi, submit representative sections in two or three tissue cas-settes. However, because the confirmation of an intrauterine pregnancy is often needed immedi-ately, it may be wise to use the following guide-line: Submit the entire specimen if it is small or as much as can be included in five tissue cassettes. Always specify the percentage of the specimen that was submitted, and include only tissue fragments. We have found that the microscopic evaluation of blood clots from intrauterine preg-nancies often does not reveal entrapped villi. If no villi are identified after your initial micro-scopic evaluation, the entire specimen may need to be submitted.
In the case of a clinically suspected molar pregnancy or the presence of hydropic villi, the submission of at least eight tissue cassettes is recommended to assess the degree of trophoblast proliferation. Any large tissue fragments, that is, fragments greater than 3 to 4 cm, should be sec-tioned and entirely submitted if they are firm, indurated, or necrotic. Consider sending fresh tissue for flow cytometric ploidy analysis or tissue culture cytogenetic analysis. Partial moles are triploid, whereas complete moles are diploid or tetraploid. Uterine resection specimens for gestational trophoblastic malignancies should be handled as for hysterectomies for endometrial or cervical cancer depending on the site of the tumor.
Second trimester therapeutic or elective abor-tion specimens may have intact placentas and fetuses. These specimens may be handled in the routine surgical pathology laboratory if the fetus is less than 500 g and/or less than 20 to 21 weeks’ gestation. however, most cases can be appropriately han-dled with a limited approach. Briefly, weigh the fetus, and measure the crown–rump, crown–heel, and foot length. Examine the external appearance for skin slippage and any gross abnormalities of structure such as missing limbs or extra digits. Open the thorax and abdomen with a vertical midline incision. Confirm the appropriate posi-tion of the internal organs, and take a piece of liver, lung, and gonads for microscopic evalua-tion. For the examination of a fetus with either chromosomal or congenital abnormalities, the reader is referred to Wigglesworth and Singer.14 The placenta can be routinely handled, as de-scribed in the next section.