A specimen collection cassette for use with a medical fluid collection system, said cassette including: a housing configured for removable attachment to the fluid collection system; a first fitting attached to the housing to which a suction line that extends from a medical/surgical site can be attached; an outlet opening formed in the housing through which fluid drawn through the first fitting is able to flow through the housing and into the fluid collection system, wherein the housing is formed with a supplemental opening that is separate from the outlet opening, the supplemental opening opening into a first void space internal to the housing, the first fitting opens into the first void space and there is a fluid path from the first void space to the housing outlet opening; a cap is removably attachable to the housing so as to seat over the supplemental opening, said cap having an inner surface that is directed to the housing first void space (1727, 2027) when the cap is attached to the housing; and a porous screen disposed in the housing between the first fitting and the outlet opening for trapping material entrained in the fluid flow through the housing, the porous screen being removably attachable to the inner surface of said cap and shaped to occupy the housing first void space so that, when the screen is attached to said cap and said cap is disposed over the supplemental opening, fluid that flows from the first fitting through the first void space to the outlet opening flows across the screen, wherein the housing comprises: a main body in which the outlet opening is formed, the main body having a surface with an aperture that is separate from the outlet opening; and a box that is removably attachable to the main body so as to seat over the surface in which the aperture is formed, the box defining the first void space and the supplemental opening, said box comprising a port that extends from the first void space and that is positioned so that, when said box is attached to the main body, there is fluid communication from the first void space into the main body of the housing through the port and the aperture, wherein said first fitting extends from the box so as to open into the first void space. a housing configured for removable attachment to the fluid collection system; a first fitting attached to the housing to which a suction line that extends from a medical/surgical site can be attached; an outlet opening formed in the housing through which fluid drawn through the first fitting is able to flow through the housing and into the fluid collection system, wherein the housing is formed with a supplemental opening that is separate from the outlet opening, the supplemental opening opening into a first void space internal to the housing, the first fitting opens into the first void space and there is a fluid path from the first void space to the housing outlet opening; a cap is removably attachable to the housing so as to seat over the supplemental opening, said cap having an inner surface that is directed to the housing first void space (1727, 2027) when the cap is attached to the housing; and a porous screen disposed in the housing between the first fitting and the outlet opening for trapping material entrained in the fluid flow through the housing, the porous screen being removably attachable to the inner surface of said cap and shaped to occupy the housing first void space so that, when the screen is attached to said cap and said cap is disposed over the supplemental opening, fluid that flows from the first fitting through the first void space to the outlet opening flows across the screen, wherein the housing comprises: a main body in which the outlet opening is formed, the main body having a surface with an aperture that is separate from the outlet opening; and a box that is removably attachable to the main body so as to seat over the surface in which the aperture is formed, the box defining the first void space and the supplemental opening, said box comprising a port that extends from the first void space and that is positioned so that, when said box is attached to the main body, there is fluid communication from the first void space into the main body of the housing through the port and the aperture, wherein said first fitting extends from the box so as to open into the first void space. a main body in which the outlet opening is formed, the main body having a surface with an aperture that is separate from the outlet opening; and a box that is removably attachable to the main body so as to seat over the surface in which the aperture is formed, the box defining the first void space and the supplemental opening, said box comprising a port that extends from the first void space and that is positioned so that, when said box is attached to the main body, there is fluid communication from the first void space into the main body of the housing through the port and the aperture, wherein said first fitting extends from the box so as to open into the first void space.